Apparatuses, memories, and methods for address decoding and selecting an access line

ABSTRACT

Apparatuses, memories, and methods for decoding memory addresses for selecting access lines in a memory are disclosed. An example apparatus includes an address decoder circuit coupled to first and second select lines, a polarity line, and an access line. The first select line is configured to provide a first voltage, the second select line is configured to provide a second voltage, and the polarity line is configured to provide a polarity signal. The address decoder circuit is configured to receive address information and further configured to couple the access line to the first select line responsive to the address information having a combination of logic levels and the polarity signal having a first logic level and further configured to couple the access line to the second select line responsive to the address information having the combination of logic levels and the polarity signal having a second logic level.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/197,539, filed Jun. 29, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/139,493, filed Dec. 23, 2013, and issued as U.S.Pat. No. 9,390,792 on Jul. 12, 2016. The aforementioned applications andpatent are incorporated herein by reference, in their entirety for anypurpose.

BACKGROUND

Conventional memory systems may comprise a low voltage select line and ahigh voltage deselect line for accessing a desired word or bit line(generally referred to as memory access lines). A selected memory accessline in an array is coupled to the select line, and non-selected memoryaccess lines are coupled to the deselect line. Conventional twotransistor decoder circuits used to select memory access lines maycomprise a p-channel field effect (PFET) transistor and an n-channelfield effect (NFET) transistor. NFET transistors may be advantageous fordelivering low voltages, and PFET transistors may be advantageous fordelivering high voltages. In the example conventional system described,the circuit works most efficiently when the NFET transistor connects theaccess line to the select line when activated, and the PFET transistorconnects the access line to the deselect line when activated.

However, with some memory technologies, for example, bi-polar resistiveRAM, it may be advantageous to allow current to pass through a memorycell in opposite directions during different phases of operation. Inthese situations, the conventional two-transistor decoder may notdeliver current efficiently for all directions of current flow. Anadditional PFET transistor may be placed in parallel with the NFETtransistor, and an additional NFET transistor may be placed in parallelwith the PFET transistor to form CMOS transmission gates to improvecurrent efficiency, but this solution would incur two additionaltransistors and two additional wires per access line. The increase incost and space required for the conventional decoder architecture may beundesirable in applications where circuit compactness and simplicity areneeded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an apparatus that includes a direct decoderaccording to an illustrative embodiment of the disclosure.

FIG. 2 is a circuit diagram of a decoder according to an illustrativeembodiment of the disclosure.

FIG. 3(1)-3(2) is a block diagram of a hierarchical decoder according toan illustrative embodiment of the disclosure.

FIG. 4 is a circuit diagram of a hierarchical decoder according to anillustrative embodiment of the disclosure.

FIG. 5 is a diagram of a memory system including a decoder according toan illustrative embodiment of the disclosure.

DETAILED DESCRIPTION

Certain details are set forth below to provide a sufficientunderstanding of embodiments of the disclosure. However, it will beclear to one having skill in the art that embodiments of the disclosuremay be practiced without these particular details. Moreover, theparticular embodiments of the present disclosure described herein areprovided by way of example and should not be used to limit the scope ofthe disclosure to these particular embodiments. In other instances,well-known circuits, control signals, timing protocols, and softwareoperations have not been shown in detail in order to avoid unnecessarilyobscuring the disclosure.

FIG. 1 illustrates an apparatus 100 including an address decoder 104according to an embodiment of the disclosure. The apparatus may be anintegrated circuit, a memory device, a memory system, etc. The addressdecoder 104 may be configured to decode an address to select an accessline for activation. The address decoder 104 may include decodercircuits 106, 116, 126, 136 coupled to a respective access line 119,129, 139, 149. Each decoder circuit 106, 116, 126, 136, is configured toreceive respective address information ADDIN0-ADDIN3. The addressinformation ADDIN0-ADDIN3 is based on the address being decoded. Eachdecoder circuit 106, 116, 126, 136 may comprise a predecode circuit 110,120, 130, 140, and a select circuit 115, 125, 135, 145. For simplicity,only four decoder circuits and access lines are shown, but more or lessmay be used. The access lines may be bit lines or word lines of a memoryarray. In some embodiments, a second address decoder (not shown inFIG. 1) may be included in the apparatus, and configured to decodeaddress information to select an access line of a second set foractivation. For example, a first address decoder may be configured todecode address information to select a word line for activation and asecond decoder may be configured to decode address information to selecta bit line for activation to access a memory cell coupled to theselected word line and bit line.

The select circuits 115, 125, 135, 145 may be coupled to respectiveaccess lines 119, 129, 139, 149 and further coupled to select line A 102and select line B 103. The select line A 102 and select line B 103 mayprovide respective voltages. Typically, when providing voltages overselect line A 102 and select line B 103, one of the voltages is higherthan the other voltage. In some embodiments, the voltages of select lineA 102 and of select line B 103 may change. The predecode circuits 110,120, 130, 140 may be coupled to polarity line 101. The polarity line 101may provide a signal to the predecode circuits 110, 120, 130, 140 tocontrol the coupling of the access lines 119, 129, 139, 149 through therespective select circuit 115, 125, 135, 145 to select lines A and B102, 103. The predecode circuits 110, 120, 130, 140 may be furtherconfigured to activate the select circuits 115, 125, 135, 145 to couplethe respective access lines 119, 129, 139, 149 to select line A 102 orselect line B 103, for example, based on the respective addressinformation ADDIN0-ADDIN3 and the polarity line 101. In someembodiments, only the selected access line 119, 129, 139, or 149, basedon the respective address information ADDIN0-ADDIN3, may be coupled toselect line A 102 or select line B 103. The remaining non-selectedaccess lines may be coupled to the remaining select line that is notcoupled to the selected access line. The address decoder 104 may beimplemented as a direct decoder in an embodiment of the disclosure.

FIG. 2 illustrates a particular illustrative embodiment of addressdecoder 104. For simplicity, only two decoder circuits 106, 116 and twoaccess lines 119, 129 are shown, but greater or fewer decoder circuitsand access lines may be included. Predecode circuit 110 includes a4-input NAND gate 201 configured to receive address information ADDIN0,represented by a 4-bit address (ADDR0-3_BAR). The output of NAND gate201 is coupled to an input of a 2-input NAND gate 205. The other inputof NAND gate 205 is coupled to control signal EVEN_BAR, which may beused during testing, but is not activated during normal operation.EVEN_BAR is at logic high (“1”) during normal operation. The output ofNAND gate 205 is coupled to an input of XOR gate 210. The second inputof XOR gate 210 is coupled to polarity line 101. The output of XOR gate210 is coupled to the gates of PFET transistor 230 and NFET transistor235 of select circuit 115. The drains of transistors 230 and 235 arecoupled together. The source of transistor 230 is coupled to select lineA 102. The source of transistor 235 is coupled to select line B 103.Access line 119 is coupled to the drains of transistors 230 and 235.Access line 119 will be coupled to select line A 102 when transistor 230is activated and coupled to select line B 103 when transistor 235 isactivated. As shown in FIG. 2, when polarity line 101 is at logic low(“0”), the decoder circuit 106 couples the access line 119 to selectline B 103 responsive to decoding an address of “0000”, and couples theaccess line 119 to select line A 102 for other addresses, and thedecoder circuit 116 couples the access line 129 to select line B 103responsive to decoding an address of “1000”, and couples the access line129 to select line A 102 for other addresses.

Similar to predecode circuit 110, predecode circuit 120 includes a4-input NAND gate 215 configured to receive address information ADDIN1,represented by a 4-bit address (ADDR0, ADDR1-3_BAR). The output of NANDgate 215 is coupled to an input of a 2-input NAND gate 220. The otherinput of NAND gate 220 is coupled to control signal ODD_BAR, which maybe used during testing, but is not activated during normal operation.ODD_BAR is at logic high during normal operation. The output of NANDgate 220 is coupled to an input of XOR gate 225. The second input of XORgate 225 is coupled to polarity line 101. The output of XOR gate 225 iscoupled to the gates of PFET transistor 240 and NFET transistor 245 ofselect circuit 125. The drains of transistors 240 and 245 are coupledtogether. The source of transistor 240 is coupled to select line A 102.The source of transistor 245 is coupled to select line B 103. Accessline 129 is coupled to the drains of transistors 240 and 245. Accessline 129 will be coupled to select line A 102 when transistor 240 isactivated and coupled to select line B 103 when transistor 245 isactivated.

The foregoing description is only one possible implementation of thedisclosure. The disclosure may be implemented with alternative logicgates and transistor types without departing from the scope of thepresent disclosure. Certain examples of circuit operation will now bedescribed. The examples described below are provided to enhanceunderstanding of the present disclosure. The examples should not beconsidered to be limiting in scope of the present disclosure.

In a first example, the address to be decoded is “0000”, which whendecoded will cause access line 119 to be selected. As a result of the“0000” address, address information ADDR0_BAR, ADDR1_BAR, ADDR2_BAR, andADDR3_BAR provided to the NAND gate 201 is “1111,” and the addressinformation ADDR0, and ADDR1-3_BAR provided to the NAND gate 215 is“0111”. As previously discussed, decoding an address of “0000” willresult in address information that will cause the decoder circuit 106 toselect the access line 119. Control signals EVEN_BAR and ODD_BAR arealso at logic high. Polarity line 101 is set to logic low. Also in thepresent example, the voltage of select line A 102 is greater than thevoltage of select line B 103.

Due to the “1111” provided to the NAND gate 201, the NAND gate 201provides a logic low output, and the output of NAND 205 is logic high.When the output of NAND gate 205 is logic high, and polarity line 101 islogic low, the output of XOR gate 210 is logic high. The logic highoutput of the XOR gate 210 activates NFET transistor 235 to couple theaccess line 119 to select line B 103. Referring to predecode circuit120, due to the “0111” provided to the NAND gate 215, the output of NANDgate 215 is logic high. Again, ODD_BAR is logic high. Consequently, theoutput of NAND gate 220 is logic low. The polarity line, as previouslydiscussed is also logic low. When both inputs are logic low, the outputof XOR gate 225 is also logic low. The logic low output of the XOR gate225 activates PFET transistor 240 to couple the access line 129 toselect line A 102.

An example where the coupling of the access lines to the select line A102 and select line B 103 through the respective select circuits isreversed will now be described. While the address information providedto the NAND gates 201 and 215, and the logic level output by NAND gates205 and 220 remain the same as previously described, the polarity line101 is now set to a logic high. That is, the output of NAND gate 201 isstill logic low, and the output of NAND gate 205 is still logic high.However, because the polarity line 101 is at a logic high, now bothinputs to XOR gate 210 are logic high, and as a result, the output ofXOR gate 210 is logic low. This activates PFET transistor 230, andaccess line 119 is coupled to select line A 102. Referring again toprecode circuit 120, the output of NAND gate 215 is still logic high dueto the “0111” provided to the NAND gate 215, and NAND gate 220 is stilllogic low. With the polarity line 101 a logic high, the output of XORgate 225 is logic high. This activates NFET transistor 240, and accessline 129 is coupled to select line B 103. As illustrated by the previousexample, the access line 119 is switched from being coupled to selectline B 103 to being coupled to select line A 102, and the access line129 is switched from being coupled to select line A 102 to being coupledto select line B 103. The address decoder 104 may change which of theselect lines the respective access line is coupled through the use ofthe polarity line 101. The XOR gate 210 may conditionally invert theoutput signal of the NAND gate 205 based on the logic level of thepolarity line 101, thus, changing which of the transistors of the selectcircuit are activated when the address information causes the NAND gate205 to provide an active output signal to the XOR gate. PFETtransistors, such as the transistor 230 of the select circuit, aretypically more suited for providing a higher voltage from a source to alower voltage at a drain, and NFET transistors, such as the transistor235 of the select circuit, are typically more suited for providing alower voltage from a source to a higher voltage at a drain. Changing avoltage to be provided to an access line may be more efficiently handledby switching hick of the transistors of the select circuit is activatedduring operation.

For example, continuing from the previous example of providing anaddress “0000” for decoding and a logic low provided on the polarityline 101, a “1111” is provided to the NAND gate 201 of the decodercircuit 106 causing the XOR gate 210 to provide a logic high signal toactivate the NFET transistor 235 and couple the access line 119 to theselect line B 103, and a “0111” is provided to the NAND gate 215 of thedecoder circuit 116 causing the XOR gate 225 to provide a logic lowsignal to activate the PFET transistor 240 and couple the access line129 to select line A 102. As previously discussed, the voltage of selectline A 102 is greater than the voltage of select line B 103 in theprevious example. Changing the select line coupled to the access linesmay be accomplished by changing the logic level of the polarity line 101from a logic low to logic high, which switches the output of the XOR,gate 210 from logic high to logic low, and switches the output of theXOR gate 225 from logic low to logic high. As a result, the access line119 is coupled to the select line A 102 and is provided the highervoltage through PFET transistor 230 and the access line 129 is coupledto the select line B 103 and is provided the lower voltage through NFETtransistor 245.

Changing to which of the select lines the access line is coupled may beused to perform memory operations that may involve switching a polarityacross a memory cell. For example, in some embodiments, the access lines119, 129 may be word lines. Similar circuits to decoder circuits 106 and116 may exist for the bit lines. The corresponding circuitry for the bitlines is not shown in FIG. 2. Operation of the decoder circuits coupledto the word lines and the decoder circuits coupled to the bit lines maybe coordinated such that the voltage across a selected memory cell maybe switched, which causes current to flow through memory elements indifferent directions. As previously discussed, in some embodiments, thevoltages of select line A 102 and of select line B 103 may change, forexample, during operation, which may provide greater flexibility inproviding different voltages or changing voltages provided to the accesslines.

In typical memory arrays, many access lines, often on the order of 1,000are implemented. More efficient decoder circuitry is desirable to reducethe number of components and the area required by the circuit. Ahierarchical decoding structure may be implemented to reduce the numberof components required in the decoder circuit. Embodiments of thepresent disclosure may also be included in a hierarchical decodingstructure. This may be desirable to amortize the overhead of thecircuitry that allows for the switching of the coupling of access linesto the select lines.

FIG. 3(1)-3(2) is a block diagram of a hierarchical address decoder 301according to an illustrative embodiment of the disclosure. The currentembodiment is described with respect to an 8-bit address (ADDR0-ADDR7)provided to the address decoder 301, allowing for decoding of up to 256access lines. However, an address of a different number of bits, and fora different number of access lines may be used without departing fromthe scope of the disclosure. One of ordinary skill in the art willappreciate that this will alter the number of predecode circuits fordecoding addresses. The hierarchical address decoder 301 may includesixteen local predecode circuits and sixteen global precode circuits.The local predecode circuits 330-345 may receive the four leastsignificant bits of an address (ADDR0-3) to provide address information.The local predecode circuits 330-345 may be coupled to polarity line101. Each local predecode circuit may be further coupled to a respectivelocal select circuit 350-365. Each local predecode circuit may befurther coupled to 15 other local select circuits (not shown). Forexample, local predecode circuit 0 330 may be coupled to local selectcircuit 0 350, local select circuit 16 (not shown), local select circuit32 (not shown), etc. Local predecode circuit 1 331 may be coupled tolocal select circuit 1 351, local select circuit 17 (not shown), localselect circuit 33 (not shown), etc. The local predecode circuits 2-15332-345 may be similarly coupled. The global predecode circuit 305 mayreceive other bits of the address, and may also be coupled to polarityline 101. The global predecode circuit 0 305 may be further coupled tolocal select circuits 350-365. Fifteen additional global predecodecircuits (not shown) may be included and coupled to the local selectcircuits. For example, local select circuits 0-15 350-365 may be coupledto global circuit 0 305, local select circuits 16-31 (not shown) may becoupled to global predecode circuit 1 (not shown), local select circuits32-47 (not shown) may be coupled to global predecode circuit 2, etc.Each local select circuit 350-365 may be coupled to select line A 102and select line B 103. Each local select circuit may be further coupledto a respective access line 370-385.

By implementing a hierarchical decoding structure, the number ofpredecode circuits may be reduced from 256 to 32. Greater efficiency maybe achieved by adding additional levels to the hierarchy for largernumbers of access lines without departing from the scope of thedisclosure.

FIG. 4 is a circuit diagram of a hierarchical address decoder 301according to an illustrative embodiment of the disclosure. For clarity,the circuitry for selecting a single access line 370 is shown, but maybe replicated for other access lines as well. Address information,represented in FIG. 4 as ADDR0-3_BAR, is received at the input of NANDgate 401. The output of NAND gate 401 is coupled to NAND gate 405. Thesecond input of NAND gate 405 is coupled to control signal EVEN_BAR,which may he used during testing, but is not activated during normaloperation. EVEN_BAR is at logic high during normal operation. The outputof NAND gate 405 is coupled to the input of XOR gate 410. The otherinput of XOR gate 410 is coupled to polarity line 101. The output of XORgate 410 is coupled to the gates of PFET transistor 455 and NFETtransistor 460 in local select circuit 350. The drains of transistors455 and 460 are coupled together and to access line 370. The source oftransistor 455 is coupled to the drains of PFET transistor 445 and NFETtransistor 450. The source of transistor 460 is coupled to the drains ofPFET transistor 465 and NFET transistor 470.

Global predecode circuit 305 receives address information, representedin FIG. 4 as ADDR4-7_BAR at the input of NAND gate 415. The output ofNAND gate 415 is coupled to the input of NAND gate 420. The other inputof NAND gate 420 is coupled to control signal ODDOREVEN_BAR, which maybe used during testing, but is not activated during normal operation.ODDOREVEN_BAR is at logic high during normal operation. The output ofNAND gate 420 is coupled to the inputs of NOR gate 425 and NOR gate 440.The second input of NOR gate 425 is coupled to polarity line 101. Theoutput of NOR gate 42.5 is coupled to the input of inverter 430. Theoutput of inverter 430 is coupled to the gates of transistors 465 and470. The drains of transistors 465 and 470 are coupled to each other,and as mentioned above, are coupled to the source of transistor 460. Thesource of transistor 465 is coupled to select line A 102, and the sourceof transistor 470 is coupled to select line B 103. Returning to NOR gate440, the second input is coupled to the output of inverter 435. Theinput of inverter 435 is coupled to polarity line 101. The output of NORgate 440 is coupled to the gates of transistors 445 and 450. The drainsof transistors 445 and 450 are coupled to each other and to the sourceof transistor 455. The source of transistor 445 is coupled to selectline A 102 and the source of transistor 450 is coupled to select line B103.

The disclosure may be implemented with alternative logic gates andtransistor types without departing from the scope of the presentdisclosure. Certain examples of circuit operation will now be described.The examples described below are provided to enhance understanding ofthe present disclosure. The examples should not be considered to belimiting in scope of the present disclosure.

In a first example, the address “0000 0000” is to be decoded. The 00000000 address corresponds to access line 370. That is, the access line370 is selected by the address 0000 0000. ADDR0_BAR, ADDR1_BAR,ADDR2_BAR, ADDR3_BAR, ADDR4_BAR, ADDR5_BAR, ADDR6_BAR, and ADDR7_BAR areall logic high (e.g., “1111 1111”). EVEN_BAR and ODDOREVEN_BAR are alsologic high, and polarity line 101 is set to logic low.

Referring to local predecode circuit 330, the output of NAND gate 401 islogic low. As mentioned above, EVEN_BAR is logic high (“1”), therefore,the output of NAND gate 405 is logic high. With the polarity line 101logic low, the output of XOR gate 410 is logic high. The output of theXOR gate 410 activates NFET transistor 460. Access line 370 is coupledto the drains of transistors 465 and 470.

Referring to global predecode circuit 305, the output of NAND gate 415is logic low. ODDOREVEN_BAR is logic high, therefore the output of NANDgate 420 is logic high. The output of NOR gate 425 is logic low, whichis inverted by inverter 430. Therefore, the signal provided totransistors 465, 470 is logic high, and NFET transistor 470 isactivated. As mentioned above, NFET transistor 460 is also activatedcausing access line 370 to be coupled to select line B 103. Returning toNOR gate 440, it receives the logic high from NAND gate 420. The logiclow of polarity line 101 is inverted by inverter 435, such that theinputs to NOR gate 440 are both logic high. This causes the output ofNOR gate 440 to be logic low, activating PFET transistor 445. However,because PFET transistor 455 is not activated, the voltage of select lineA 102 is not provided to the access line 370.

An example where the coupling of access line 370 to a select line isreversed, will now be described. The logic level of the polarity line101 is changed from logic low to logic high. The output of the NAND gate405 and the output of NAND gate 420 are still at logic high. In thisexample, the output of XOR gate 410 will be logic low, and PFETtransistor 455 will be activated. Access line 370 will be coupled byPFET transistor 455 to the drains of transistors 445 and 450. The outputof NOR gate 425 is logic low and is inverted by inverter 430. Therefore,the signal provided to the transistors 465, 470 is logic high, and NFETtransistor 470 is activated. However, because transistor 460 is notactivated, the voltage of select line B 103 is not provided to theaccess line 370. Returning to NOR gate 440, it receives the logic highfrom NAND gate 420. With the polarity line 101 set to a logic high, andinverted by inverter 435, the input to NOR gate 440 is logic low. Thusthe output of NOR gate 440 is logic low, activating PFET transistor 445.As mentioned above, PFET transistor 455 is also activated causing accessline 370 to be coupled to select line A 102.

In some embodiments, the ability to switch to which select line anaccess line is coupled without deselecting or further re-selecting theaccess line may provide greater flexibility in providing differentvoltages or changing voltages provided to the access lines. As describedin the above example, the select line coupled to the access line may beswitched by changing the logic signal on the polarity line 101, whichalters which transistors are activated. The address decoder 301 may notneed to wait for a new address to decode and switch to which select linethe selected access line is coupled.

In the above example, access line 370 may be one of a plurality of wordlines. Similar circuits to local predecode circuit 330, global predecodecircuit 305, and local select circuit 350 may exist for a plurality ofbit lines. For clarity, the corresponding circuitry for the bit lines isnot shown. When the coupling of the access line 370 to the select linesis switched, and polarity line 101 is switched from logic low to logichigh, the coupling of the bit lines to the select lines may also bereversed. The result of this coordinated reversal of polarity of selectlines for both the word lines and bit lines, aided by the global signalpolarity line 101, is that current may be able to efficiently flowthrough memory elements in different directions.

FIG. 5 is a block diagram of a memory system including an addressdecoder according to an embodiment of the disclosure. The memory systemincludes a memory 903 according to an embodiment of the disclosure.Memory system 901 includes a memory access device 911 (e.g., processor,memory controller, etc.) coupled to the memory 903.

The memory 903 includes a memory array 913 of memory cells. The memoryarray 913 may include, for example, volatile memory cells (e.g., DRAMmemory cells, SRAM memory cells), non-volatile memory cells (e.g., flashmemory cells), or some other types of memory cells. In an embodiment ofthe disclosure, the memory array 913 includes non-volatile resistivememory cells, and the memory 903 is a resistive random access memoryRRAM. The memory 903 and memory access device 911, can be implemented asseparate integrated circuits, or the memory access device 911 and thememory 903 can be incorporated into the same integrated circuit, chip,or package. The memory access device 911 can be a discrete device (e.g.,microprocessor) or some other type of process circuitry implemented infirmware, such as an application-specific integrated circuit (ASIC).

I/O connections 927 and control connections 929 include a communicationinterface between the memory access device 911 and the memory 903. Theembodiment of FIG. 5 includes address circuitry 943 to latch addresssignals provided over the I/O connections 927 through I/O controlcircuitry 919. Address signals are received and decoded by a row addressdecoder circuit 957 and a column address decoder circuit 951 to accessthe memory array 913. The row address decoder circuit 957 and/or thecolumn address decoder circuit 951 may include an address decoder 952,959 in accordance with one or more embodiments of the disclosure. Inlight of the present disclosure, it will be appreciated by those havingordinary skill in the art that the number of address input connectionsdepends on the density and architecture of the memory array 913 and thatthe number of addresses increases with both increased numbers of memorycells per memory array, an increased number of memory blocks, and/or anincreased number of memory arrays. The reader will also appreciate thatmore address information may be needed to specify a particular portionof the memory array as the size of the memory array increases.

The read circuitry 953 can read data from the memory array 913. I/Ocontrol circuitry 919 is included for bi-directional data communicationover the 110 connections 927 with the memory access device 911. Writecircuitry 955 is included to write data to the memory array 913.

Control logic circuitry 921 decodes signals provided by controlconnections 929 from the memory access device 911. These signals caninclude chip signals, write enable signals, and address latch signalsthat are used to control the operations on the memory 903, and of thememory array 913, including data reading and data writing. The controllogic circuitry 921 may provide a signal to the polarity line (notshown) and control the polarity of the select lines (not shown) suchthat current may be allowed to flow in different directions throughcertain memory cells during different phases of operation.

The control logic circuitry 921 can send signals to selectively setparticular registers and/or sections of registers, or latch data in oneor more registers. In one or more embodiments, the control logiccircuitry 921 is responsible for executing instructions received fromthe memory access device 911 to perform certain operations on someportion of the memory cells of the memory array 913. The control logiccircuitry 921 can be a state machine, a sequencer, or some other type oflogic controller. It will be appreciated by those having ordinary skillin the art that additional circuitry and control signals can beprovided, and that the memory device detail of FIG. 5 has been reducedto facilitate ease of illustration.

Those of ordinary skill would further appreciate that the variousillustrative logical blocks, configurations, modules, circuits, andalgorithm steps described in connection with the embodiments disclosedherein may be implemented as electronic hardware, computer softwareexecuted by a processor, or combinations of both. Various illustrativecomponents, blocks, configurations, modules, circuits, and steps havebeen described above generally in terms of their functionality. Whethersuch functionality is implemented as hardware or processor executableinstructions depends on the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

The previous description of the disclosed embodiments is provided toenable a person skilled in the art to make or use the disclosedembodiments. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the principles defined hereinmay be applied to other embodiments without departing from the scope ofthe disclosure. Thus, the present disclosure is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope possible consistent with the principles and novel features asdefined by the following claims.

What is claimed is:
 1. A method, comprising: receiving addressinformation corresponding to an access line associated with an addressdecoder circuit; receiving a polarity signal with the address decodercircuit; coupling the access line to at least one of a first select lineor a second select line, based, at least in part, on the addressinformation and the polarity signal having a first logic level; andswitching the coupling of the access line to the at least one of thefirst select line or the second select line, based, at least in part, onthe address information and the polarity signal having a second logiclevel.
 2. The method of claim 1, further comprising providing an outputsignal having a first value responsive to the address information havinga combination of logic levels and the polarity signal having a firstpolarity value, the output signal having a second value responsive tothe address information having the combination of logic levels and thepolarity signal having a second polarity value.
 3. The method of claim2, further comprising applying at least one of a first voltage or asecond voltage based, at least in part, on whether the output signal hasthe first value or the second value.
 4. The method of claim 3, furthercomprising coupling the output signal to a gate of a first transistorand a gate of a second transistor.
 5. The method of claim 4, furthercomprising applying the first voltage and the second voltage at sourceterminals of the first transistor and the second transistor,respectively.
 6. The method of claim 5, further comprising coupling adrain of the second transistor to the access line.
 7. The method ofclaim 1, further comprising: receiving an address corresponding to asecond access line with a second address decoder circuit; receiving asignal with the second address decoder circuit indicating a polarity ofa third select, line and a fourth select line; and coupling the secondaccess line with the second address decoder circuit to at least one ofthe third or fourth select tine, based at least in part, on the addresscorresponding to the second access line and the polarity signal.
 8. Themethod of claim 7 wherein a memory cell is coupled to the access lineand the second access line.
 9. The method of claim 8 further comprising,flowing current through the memory cell in a direction, the direction ofthe current based, at least in part, on a logic level of the polarityline.
 10. The method of claim 8, further comprising switching voltagesof the first and second select lines.
 11. An apparatus, comprising: apredecode circuit configured to receive address information and apolarity signal, the predecode circuit operable to provide an outputsignal having a first value responsive to the address information havinga combination of logic levels, the polarity signal having a firstpolarity value and the output signal having a second value responsive tothe address information having the combination of logic levels and thepolarity signal having a second polarity value; and a select circuitconfigured to receive the output signal, the select circuit operable toprovide a voltage having a first polarity responsive to the outputsignal having the first value and a second polarity responsive to theoutput signal having the second value.
 12. The apparatus of claim 11,wherein the predecode circuit comprises a plurality of logic gatesconfigured to provide the output signal having the first value.
 13. Theapparatus of claim 12, wherein the select circuit comprises a firsttransistor and a second transistor, the output signal of the pluralityof logic gates coupled to a gate of the first transistor and a gate ofthe second transistor.
 14. The apparatus of claim 13, wherein the firsttransistor is a p-type transistor.
 15. The apparatus of claim 13,wherein the second transistor is an n-type transistor.
 16. The apparatusof claim 13, wherein a source of the first transistor is coupled to asource of the first voltage and a source of the second transistor iscoupled to a source of the second voltage.
 17. The apparatus of claim13, wherein the predecode circuit is coupled to a polarity line.
 18. Theapparatus of claim 17, wherein the predecode circuit comprises an XORgate having a first input terminal coupled to the polarity line, theplurality of logic gates configured to decode the address informationand provide a signal to a second input terminal of the XOR gate.
 19. Theapparatus of claim 13, wherein the select circuit is coupled to thepredecode circuit and to an access line.
 20. The apparatus of claim 19,wherein a drain of the first transistor is coupled to a drain of thesecond transistor and to the access line.